/* Read-only tables for Lua */

#include <string.h>
#include "lrotable.h"
#include "lua.h"
#include "lauxlib.h"
#include "lstring.h"
#include "lobject.h"
#include "lapi.h"

/* Local defines */
#define LUAR_FINDFUNCTION     0
#define LUAR_FINDVALUE        1

/* Externally defined read-only table array */
extern const luaR_table lua_rotable[];

/* Find a global "read only table" in the constant lua_rotable array */
void *luaR_findglobal(const char *name, unsigned len)
{
    unsigned i;

    if (strlen(name) > LUA_MAX_ROTABLE_NAME)
        return NULL;
    for (i = 0; lua_rotable[i].name; i ++)
        if (*lua_rotable[i].name != '\0' && strlen(lua_rotable[i].name) == len && !strncmp(lua_rotable[i].name, name, len))
        {
            return (void *)(lua_rotable[i].pentries);
        }
    return NULL;
}

/* Find an entry in a rotable and return it */
static const TValue *luaR_auxfind(const luaR_entry *pentry, const char *strkey, luaR_numkey numkey, unsigned *ppos)
{
    const TValue *res = NULL;
    unsigned i = 0;

    if (pentry == NULL)
        return NULL;
    while (pentry->key.type != LUA_TNIL)
    {
        if ((strkey && (pentry->key.type == LUA_TSTRING) && (!strcmp(pentry->key.id.strkey, strkey))) ||
                (!strkey && (pentry->key.type == LUA_TNUMBER) && ((luaR_numkey)pentry->key.id.numkey == numkey)))
        {
            res = &pentry->value;
            break;
        }
        i ++;
        pentry ++;
    }
    if (res && ppos)
        *ppos = i;
    return res;
}

int luaR_findfunction(lua_State *L, const luaR_entry *ptable)
{
    const TValue *res = NULL;
    const char *key = luaL_checkstring(L, 2);

    res = luaR_auxfind(ptable, key, 0, NULL);
    if (res && ttislightfunction(res))
    {
        luaA_pushobject(L, res);
        return 1;
    }
    else
        return 0;
}

/* Find an entry in a rotable and return its type
   If "strkey" is not NULL, the function will look for a string key,
   otherwise it will look for a number key */
const TValue *luaR_findentry(void *data, const char *strkey, luaR_numkey numkey, unsigned *ppos)
{
    return luaR_auxfind((const luaR_entry *)data, strkey, numkey, ppos);
}

/* Find the metatable of a given table */
void *luaR_getmeta(void *data)
{
#ifdef LUA_META_ROTABLES
    const TValue *res = luaR_auxfind((const luaR_entry *)data, "__metatable", 0, NULL);
    return res && ttisrotable(res) ? rvalue(res) : NULL;
#else
    return NULL;
#endif
}

static void luaR_next_helper(lua_State *L, const luaR_entry *pentries, int pos, TValue *key, TValue *val)
{
    setnilvalue(key);
    setnilvalue(val);
    if (pentries[pos].key.type != LUA_TNIL)
    {
        /* Found an entry */
        if (pentries[pos].key.type == LUA_TSTRING)
            setsvalue(L, key, luaS_newro(L, pentries[pos].key.id.strkey))
            else
                setnvalue(key, (lua_Number)pentries[pos].key.id.numkey)
                setobj2s(L, val, &pentries[pos].value);
    }
}
/* next (used for iteration) */
void luaR_next(lua_State *L, void *data, TValue *key, TValue *val)
{
    const luaR_entry *pentries = (const luaR_entry *)data;
    char strkey[LUA_MAX_ROTABLE_NAME + 1], *pstrkey = NULL;
    luaR_numkey numkey = 0;
    unsigned keypos;

    /* Special case: if key is nil, return the first element of the rotable */
    if (ttisnil(key))
        luaR_next_helper(L, pentries, 0, key, val);
    else if (ttisstring(key) || ttisnumber(key))
    {
        /* Find the previoud key again */
        if (ttisstring(key))
        {
            luaR_getcstr(strkey, rawtsvalue(key), LUA_MAX_ROTABLE_NAME);
            pstrkey = strkey;
        }
        else
            numkey = (luaR_numkey)nvalue(key);
        luaR_findentry(data, pstrkey, numkey, &keypos);
        /* Advance to next key */
        keypos ++;
        luaR_next_helper(L, pentries, keypos, key, val);
    }
}

/* Convert a Lua string to a C string */
void luaR_getcstr(char *dest, const TString *src, size_t maxsize)
{
    if (src->tsv.len + 1 > maxsize)
        dest[0] = '\0';
    else
    {
        memcpy(dest, getstr(src), src->tsv.len);
        dest[src->tsv.len] = '\0';
    }
}

/* Return 1 if the given pointer is a rotable */
#ifdef LUA_META_ROTABLES

#include "compiler.h"

int luaR_isrotable(void *p)
{
    return RODATA_START_ADDRESS <= (char *)p && (char *)p <= RODATA_END_ADDRESS;
}
#endif
